Light projecting arrangement



y 1964 R. GUNTHER ETAL 3,133,219

LIGHT PROJECTING ARRANGlFiMENT Filed Feb. 27. 1961 INVENT'OIQ I 5 W W f 2 xm United States Patent 3,133,219 LIGHT PROJECTRNG ARRANGEMENT Rainer Gunther and Albrecht Kaltenhiiuser, Frankfurt am Main, Germany, assignors to Trilux Lenze K.-G.,

Neheim-Husten, Germany Filed Feb. 27, 1961, Ser. No. 91,994 Claims priority, application Germany Feb. 26, 1960 4 Claims. ((31. 31354) 7 The present invention concerns a light projecting arrangement which term is intended to include, in the following specification and claims, at least such devices as search lights, spot lights, flood lights, headlights and signal lights. Conventionally, devices of this character include optical elements for controlling the direction or orientation, also the convergence, the parallelism or the divergence of beams of light emitted from the particular device, these optical elements being for instance either lenses or reflectors or both.

The class of light projecting arrangements dealt with herebelow does not require the continuous introduction or consumption of a fuel or of electric current, but is based on the use of light emitting means which include a radioactive substance as source of energy and a luminescent substance which is excited by radiation emanating from the radioactive substance so as to emit light. A typical and suitable radioactive substance is the Well known group of radioactive isotopes emitting constantly radiation during their slow disintegration. A typical example of well known luminescent substances is phosphorescent zinc sulfide. The term light in the following specification and claims is to be interpreted broadly as covering radiation in the spectral range encompassing the ultraviolet, and the visible and the ultrared portions of the spectrum. a

If it is desired to use the light derived from light emitting means including a radioactive substance as source of energy for producing in a projecting arrangement predetermined types of light beams, then it will be found that it is quite diflicult to reconcile various conditions and requirements.

If a satisfactory arrangement of light rays in a beam is to be obtained, it is necessary to have a light source of rather small dimensions in relation to the dimensions of the pertaining reflector. Therefore, if excessively large reflectors and correspondingly unwieldy assemblies are to be avoided, only relatively small space is available for the actual source of light. In particular, if radioactive isotopes are to be used as the source of energy for the light emission the first difliculty arises from the problem of how to accommodate in a practically useful light projecting arrangement the quantity of radioactive substance required for the operation of the arrangement.

A second difficulty arises from the fact that it is necessary to render harmless the high energy, biologically harmful radiation of light sources energized by radioactive substances. If one were to attempt to surround a projector, having a conventional reflector and operating with a light source energized by a radioactive substance, with a thick-walled, radiation blocking housing then the whole assembly would necssarily be extremely unwieldy, heavy and generally unsuitable for general use because the bulk and consequently the weight of the protective enclosure would increase in proportion with the surface area of the spaces to be surrounded or enclosed thereby, and also in proportion with the operative energy of the radiation to be blocked.

It is therefore a main object of the invention to provide for a light projecting arrangement utilizing a radioactive substance as source of energy and luminescent material energized by said source, but offering a satisfactory solution of the above mentioned problems and difiiculties.

In it is another object of the invention to provide for a light projecting arrangement of the type set forth which is comparatively easy to be commercially manufactured and reliable and eflicient in operation.

With above objects in view, a light projecting arrangement according to the invention comprises, in combination, light emitting means including a radioactive substance as source of energy for generating luminescence; light reflecting means exposed to light emitted by said light emit-ting means for giving said light a predetermined orientation; and a body of solid, transparent material bounded over part of its surface by said light reflecting means and substantially surrounding said light emitting means.

Accordingly, the body of solid material filling wholly or at least partly the space surrounded by the light reflecting means is completely suitable to serve as the body of the whole light projecting arrangement eliminating thereby substantially the need for other structural elements. One portion of the outer surface of this body may be formed to comply with the desired reflection eifect, i.e. having for instance a parabolic or elliptic axial cross-section, the surface being either self-reflecting or provided with a layer or lining having reflecting qualities, for instance of metals conventionally used for mirrors and reflectors. The remaining portion of the outer surface of the above-mentioned body, located opposite to the above described reflecting surface, may serve, as a Whole or in part, to permit the reflected light to emerge from the arrangement. This last mentioned surface may be either flat or have an optical shape to serve as a lens.

Preferably, a hollow chamber is provided within the body of solid, transparent material for accommodating the source of light. For example, the source of light may be constituted of a radioactive substance accommodated in the chamber while a luminescent material is applied to the wall surfaces of the chamber or incorporated in the wall surface layer thereof so as to be excited by the radioactive substance to emit light. In a specific modification of the arrangement, the radioactive substance is a radioactive gas introduced under elevated pressure into the chamber through a suitable channel leading from the non-reflecting surface of the solid body into the chamber. In this case the body of solid, transparent material must have suflicient mechanical strength to withstand the gas pressure.

The source of light may also consist of an intimate combination of a radioactive isotope with a luminescent substance which combination may be either a physical or chemical composition. For example, a physical composition of this type may consist of the radioactive isotope Pm or Kr or Sr and a luminescent material, eg 2118 or CaWO in proportions ranging between 121000 and 1000: l. A suitable chemical composition might consist of ZnS or Sr WO or Ca WO' The particular composition may be supplemented by the admixture of a bindermaterial, e.g. sodium silicate solution, and this mixture may be used in a quantity so as to fill com pletely the chamber, however, if the quantity is reduced so that the chamber is only partly filled by the mixture or composition the remaining space within the chamber may be used for accommodating additionally a radioactive isotope substance in any one of the possible states of aggregation. It is also possible according to the invention to arrange the luminescent substance and the isotope, with or without the addition of a binder, along the wall surfaces of the chamber or within the surface layer of the chamber walls, in which case again additional radioactive isotope material may be accommodated in the remaining empty space of the chamber.

The above mentioned chamber may also be subdivided into compartments of any desired and suitable shape in which case the above remarks concerning the type and arrangement of the light source apply analogously to the individual compartments as explained above for the entire chamber.

The invention further permits of providing for a solid, transparent body of the type mentioned above which has an inhomogenous structure by being composed of layers or portions of different materials, the portion or layer near the area of the source of light having the predominating characteristic of not changing color under the infiuence of radiation from the radioactive source, while the outer layer or portion has above all the characteristic of shielding or blocking undesired or dangerous radiation and/or of mechanical strength.

The material for the inner layer or portion may be a glass containing cer or transparent synthetic material of a group consisting of polystyrene while the outer portion or layer may be glass containing lead or uranium or again transparent synthetic material of a group consisting of perspex.

To improve the features of said transparent body, zones containing a dense but light transparent solution as for example of zinc bromide in water may be installed.

Thus the invention makes it possible to produce light projecting arrangements like searchlights, spotlights, floodlights, headlights, signal lights and the like having comparatively small overall dimensions yet a substantial light output which comply fully with practical illumination requirements and with the requirement of protection against harmful radiation. The above mentioned body of solid, transparent material constitutes simultaneously an enclosure for the source of light and the body of the entire light projecting arrangement. In this manner it is possible to give to the enclosure containing the source of light a great mechanical strength which is only limited by the overall dimensions of the entire arrangement. Conse quently, it is possible to introduce into the chamber inside the body not only solid radioactive isotopes but also gaseous isotopes, e.g. krypton 85, tritium or xenon 133, either alone or in combination with a solid isotope, under elevated pressure whereby the gas is concentrated and the active radiation and the resulting light output are substantially increased.

To arrange the radioactive isotope and the luminescent within the surface layer of the chamber walls the chamber Wall may consist of an organic material, e.g. polystyrene, in which is chemically built in tritium or C and in which is physically embedded ZnS.

It can be seen that the material of the solid, transparent body acts as a shield against the high energy radiation from the radioactive substance, including primary a, )3, and 'y-radiation and bremsstrahlung arising from stopping of betas. The shielding effect starts immediately at the wall surface of the chamber which contains the radioactive substance so that in this manner much less shielding material is required as compared with a construction in which a shield would have to be built around the comparatively large volume of the entire light projecting arrangement. Consequently, the overall dimensions of the light projecting arrangement according to the invention are remarkably reduced. Since in the arrangement according to the invention the shielding material extends from the source of light as far as to the light reflecting surface or layer, the shielding effect of the body increases with an increase of the size of the source of light and with the corresponding increase of the size of the reflecting surface or layer because the amount of shielding material between the source and the reflecting surface necessarily increases accordingly.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which a preferred embodiment of the invention is illustrated.

The body 1 of solid transparent material, e.g. glass or transparent synthetic material of the type described above, is shown in cross section with a curved contour 3 which may be parabolic or elliptic, on one side, and a straight contour 5, on the other side. The body 1 may be a body of revolution with respect to the axis 2 so that the surface represented by the contour 3 is e.g. a paraboloid or ellipsoid. The surface represented by the contour 3 may be such that it effects reflection or total reflection. The rays of light reflected by this surface are caused to emerge from the body 1 through the front surface 5 which, instead of being flat, as shown, may be curved to act as a lens. The reflective capacity of the surface at 3 may be increased by the application of a layer 4 of reflecting metal. Within the body 1 is provided a chamber 6 the center of which may be located preferably in a focal point of the reflecting surface illustrated by the contour 3, or in another desired point defined in relation to the reflecting surface at 3 or/and the front surface 5 depending upon which arrangement of the light rays emanating from the front surface as a beam or beams is to be obtained. In the illustrated example the wall surface of the chamber 6 is provided with a layer 7 of luminescent material leaving a central space for accommodating a radioactive substance, not shown. Of course, the illustration applies analogously to that modification of the invention in which either the luminescent material alone or a combination thereof with the radioactive substance is applied to the wall of the chamber 6 or located within the surface layer of this wall.

For introducing the luminescent material and the radioactive substance or a combination thereof, the radioactive substance being eithcr solid, liquid or gaseous, a channel 10 is provided leading from the front surface 5 into the chamber 6 and suitably closed by a stopper 11.

As mentioned above, the body 1 may be composed of layers or portions of different materials but evidently it is not necessary to illustrate this in the drawing.

If, however, the body 1 is composed of different layers or portions of materials having the above mentioned different characteristics, it is also possible to provide for at least one layer or portion which has specific optical characteristics, for instance the capability of filtering certain portions of the spectral range of the emitted light which may, for instance, determine the color of the emitted light, or for instance diffraction of certain portions of the main beam into different directions.

Evidently the illustration can be considered as showing an embodiment of the invention in which the body 1 is not a body of revolution but a different geometrical body as a parabolic or elliptic cylinder having a longitudinal axis perpendicular to the plane of the drawing. In such case the chamber 6 would assume the form of a tubular space having an axis which coincides or may coincide with the focal line of the reflecting surface represented by the contour 3.

As can be seen, the arrangement according to the invention yields the following advantages:

The mechanical stability of the light projecting arrangement is remarkably increased.

The position of the source of light with respect to the reflecting surface is invariably fixed.

Even by rough and careless handling of the light projecting arrangement it is practically impossible to release the radioactive substance unintentionally.

The reflecting means are protected against deterioration of their reflecting capacity on account of being bombarded by high energy radiation because the solid body of transparent material is interposed between the source of light and the reflecting means.

The number of necessary components of the whole arrangement is greatly reduced as compared with other projectors.

It will be understood that each of the elements described above or two or more together, may also find a useful application in other types of a light projecting arrangement differing from the types described above.

While the invention has been illustrated and described as embodied in a light projecting arrangement having a radioactive substance as source of energy, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed and desired to be secured by Letters Patent is:

1. A light projecting arrangement, comprising, in combination,

light emitting means including a radioactive substance as source of energy for generating luminescence; and projector body means comprising a body of solid, transparent material provided with an inner chamber spaced in all directions from the outer surfaces of said body and substantially surrounded by the latter, said body holding said light emitting means within said chamber, at least a portion of said material located between said chamber and said outer surfaces having the ability of absorbing radioactive radiation, and one portion of said surfaces being so formed that light rays emanating from said light emitting means and reflected at said one portion are directed through a second portion of said surfaces with a predetermined orientation substantially common to said reflected rays.

2. A light projecting arrangement, comprising, in combination,

light emitting means including a radioactive substance as source of energy for generating uminescence; and

projector body means comprising a body of solid, transparent material provided with an inner chamber spaced in all directions from the outer surfaces of said body and substantially surrounded by the latter, said body holding said light emitting means within said chamber, at least a portion of said material located betwen said chamber and said outer surfaces having the ability of absorbing radioactive radiation, and one portion of said surfaces being with parabolical contour, and opaque reflecting means extending along said reflector-shaped surface portion and covering the same so that light rays emanating from said light emitting means are reflected thereby and directed through said transparent portion of said surfaces with a predetermined orientation substantially common to said reflected rays.

3. A light projecting arrangement, comprising, in combination,

light emitting means including a radioactive substance as source of energy for generating luminescence; and

projector body means comprising a body of solid, transparent materialprovided with an inner chamber spaced in all directions from the outer surfaces of said body and substantially surrounded by the latter, said body holding said light emitting means within said chamber, at least a portion of said material located betwen said chamber and said outer surface having the ability of absorbing radioactive radiation, one portion of said surfaces being transparent and another portion being reflector-shaped with parabolical contour, and opaque reflecting means extending along said reflector-shaped surface portion and covering the same so that light rays emanating from said light emitting means are reflected thereby and directed through said transparent portion of said surfaces with a predetermined orientation substantially common to said reflected rays, said transparent portion being shaped as an optical lens.

4. A light projecting arrangement, comprising, in combination,

light emitting means including a radioactive substance as source of energy for generating luminescence; and

projector body means comprising an elongated body of solid, transparent material provided with an inner chamber spaced in all directions from the outer surfaces of said body and substantially surrounded by the latter, said body holding said light emitting means within said chamber, at least a portion of said material located between said chamber and said outer surfaces having the ability of absorbing radioactive radiation, one portion of said surfaces being transparent and another portion being reflectorshaped in the form of a partial elliptical cylinder, and opaque reflecting means extending along said reflector-shaped surface portion and covering the same so that light rays emanating from said light emitting means are reflected thereby and directed through said transparent portion of said surfaces With a predetermined orientation substantially common to said reflected rays.

References Cited in the file of this patent UNITED STATES PATENTS 2,919,361 Tschakert Dec. 29, 1959 2,953,684 MacHutchin et al. Sept. 20, 1960 3,005,102 MacI-lutchin et al. Oct. 17, 1961 

1. A LIGHT PROJECTING ARRANGEMENT, COMPRISING, IN COMBINATION, LIGHT EMITTING MEANS INCLUDING A RADIOACTIVE SUBSTANCE AS SOURCE OF ENERGY FOR GENERATING LUMINESCENCE; AND PROJECTOR BODY MEANS COMPRISING A BODY OF SOLID, TRANSPARENT MATERIAL PROVIDED WITH AN INNER CHAMBER SPACED IN ALL DIRECTIONS FROM THE OUTER SURFACES OF SAID BODY HOLDING SAID LIGHT EMITTING MEANS WITHIN SAID CHAMBER, AT LEAST A PORTION OF SAID MATERIAL LOCATED BETWEEN SAID CHAMBER ADN SAID OUTER SURFACES HAVINT THE ABILITY OF ABSORBING RADIOACTIVE RADIATION, AND ONE PORTION F SAID SURFACES BEING SO FORMED THAT LIGHT RAYS EMANATING FROMSAID LIGHT EMITTING MEANS AND REFLECTED AT SAID ONE PORTION ARE DIRECTED THROUGH A SECOND PORTION OF SAID SURFACES WITH A PREDETERMINED ORIENTATION SUBSTANTIALLY COMMON TO SAID REFLECTED RAYS. 